The present invention relates to a pneumatic tire and a wheel rim, more particularly to an improved device to reduce a running noise due to air resonance in the tire cavity.
In recent years, as the noise of automobiles remarkably decreases, there is a strong demand for low noise tires. A pneumatic tire makes various types of noises. For example, a noise which is generated during running on rough asphalt roads and sounds as xe2x80x9cGHOxe2x80x9d in the inside of the car is called road noise. The frequency of the road noise ranges from 50 to 400 Hz, and the power spectrum thereof has a peak around about 250 Hz in case of passenger car tire size. This frequency corresponds to a primary mode of air resonance of the tire cavity around the tire circumference. It is possible to effectively reduce the road noise by controlling such air resonance of the tire cavity.
In the laid-open Japanese Patent application JP-A-63-137005, a tire and rim assembly is disclosed, wherein an elastic blocker is disposed in the tire cavity to prevent the air resonance. An example of the blocker is an elastic plate which extends into the tire cavity from its holder fixed to the wheel rim. Another example of the blocker is an elastic ball-like body put in the tire cavity. As the blocker occupies 40% or more of the cross sectional area of the tire cavity, it is difficulty to mount the tire on a wheel rim.
It is therefore, an object of the present invention to provide a pneumatic tire and a wheel rim in which the tire can be mounted on the wheel rim without difficulty and the tire cavity is prevented from air resonance to reduce the road noise.
According to one aspect of the present invention, a pneumatic tire comprises a tread portion, a pair of sidewall portions, a pair of bead portions, wherein lawn-like materials are provided on an inner surface of the tire.
According to another aspect of the present invention, a wheel rim for a pneumatic tire comprises a pair of bead seats for tire beads and a rim well therebetween for mounting the tire, wherein lawn-like materials are provided on a bottom of said rim well.